Pete - I don't have a 4480s to look at, but suspect you are correct.

The 965s (up to 1956 engines) has ported vaccuum, as do the W-1's.

The 3211s (for 1957 and newer engines) has manifold vaccuum.

Carter specified the 4480s for use on Chevrolet engines 1963~1967.

I don't have a 1957 or newer Rochester B to look at.

At this point in time, you need a "distributor guy", not a "carburetor guy".

I cannot advise you on the advantages/disadvantages of ported vs manifold vaccuum.

Good carburetion is fuelish hot air
The most expensive carburetor is the wrong one you attempt to modify.
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